A challenge faced by an athlete when competing and training, particularly in moderate to hot temperature conditions, is thermal energy dissipation (i.e., heat transfer). An athlete may generate substantial thermal energy as a result of physical activity. In an effort to counteract the generation of heat, the body relies on a mechanism based on evaporative cooling. Generally, when a body's core temperature rises to a certain level, the body will begin to sweat. When liquid sweat evaporates in ambient air surrounding or passing the body, the physical conversion of the liquid to a corresponding gas form (i.e., drying process) draws heat from the body. In this case, sweating cools an athlete due to an evaporative cooling effect as the sweat dries.
Evaporation of sweat is dependent on the water vapor pressure (e.g., relative humidity) of air in contact with the athlete's skin. Consequently, air movement along the athlete's skin is also an import factor in dissipating thermal energy from the athlete. For example, ambient air gains humidity as it picks up moisture during the evaporation of sweat. In the absence of adequate air movement (e.g., exchange of air along the skin), this humidified air becomes less effective at dissipating heat as it is trapped in areas surrounding the skin. As a result, reduced or minimized airflow along the skin's surface inhibits the cooling provided by continued evaporation of sweat.